1. Field of the Invention
The present invention relates to a reusable printing sheet from which prior printing deposits are readily removable. In particular, the present invention relates to a surface coating fixed to a substrate sheet which is used in an office automation equipment such as a printer of a computer or a word processor, a copier, and so on, and from a surface of which, deposits such as a printing ink or a toner are readily removed by washing with water so that the sheet can be repeatedly cleaned and used.
2. Description of the Related Art
Office automation sheets such as printing papers, copying papers, overhead projector (OHP) sheets are used in a large volume for printing characters or drawings by a xerographic copier, a laser printer, an ink jet printer, and so on. In these years, the amount of color printing is increasing. Accordingly, the volume of the office automation sheets increases year by year.
Most of the office automation sheets are discarded after use, and cause environmental problems or waste of natural resources. To solve such problems, it is preferable to recycle the once used office automation sheets, erase the printed characters or drawings, and reuse the sheets.
However, in many cases, a toner or an ink to be printed by the xerographic copier or the printer is insoluble in water, so that the removal of the toner or ink from the sheet is difficult. If the toner or ink is water-soluble, it is not easy to completely remove it from the sheet and to reuse the cleaned sheet. If an organic solvent is used to erase the printed characters or drawings, it has an adverse effect on human bodies and environment.
As one of the ways to solve such problems, EP-A-601-502 (corresponding to JP-A-6-222604) disclose an office automation sheet having a surface coating comprising a hydrophilic resin which swells in water but is not washed off by water and is a solid in air at ambient temperatures. The disclosed office automation sheet is useful, but still unsatisfactory, since its printing property with the toner or ink, its transportability in the copying or printing machine, and its easy handling property may be deteriorated after recycling.